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BMS 242 - CVS respiratory > Cardiac cycle > Flashcards

Cardiac cycle Flashcards

(63 cards)

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1
Q

What are the 4 major stages of the cardiac cycle?

When does each stage occur?

A

1) INFLOW phase (into the ventricles)
2) ISOVOLUMETRIC CONTRACTION
3) OUTFLOW phase (out of the ventricles)
4) ISOVOLUMETRIC RELAXATION

Stages 1 and 4 - during DIASTOLE
Stages 2 and 3 - during SYSTOLE

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2
Q

What happens in the inflow phase of the cardiac cycle?

A

Blood ENTERS the heart

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3
Q

What happens in the isovolumetric contraction of the cardiac cycle?

A

Contraction where the VOLUME of the heart stays the SAME

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4
Q

What happens in the outflow phase of the cardiac cycle?

A

Blood from the heart to the lungs or systemic system

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5
Q

What happens in the isovolumetric relaxation of the cardiac cycle?

A

Relaxation of the heart where the VOLUME of the ventricles stays the SAME

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6
Q

What is diastole?

What happens during diastole?

A

Heart RELAXING

Ventricles FILL with blood

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7
Q

What is systole?

A

Heart CONTRACTING

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8
Q

Describe the movements through the valves of the heart

A

Passive

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9
Q

What is LVDEV?

A

Left ventricular diastolic end volume

Volume in the left ventricle at the end of diastole

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10
Q

What is LVSEV?

A

Left ventricular systolic end volume

Volume in the left ventricle at the end of systole

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11
Q

What initiates the cardiac cycle?

A

P wave

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12
Q

How do both atria contract simultaneously?

A

Fast conduction velocity in the BRACHMNN’S BRANCH - takes the electrical signal to the left atria

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13
Q

What does atrial contraction cause?

A
  • Increase in blood pressure in both atria
  • Forcing the valves open
  • Squeezing the blood into the ventricles
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14
Q

How does 80% of blood flow into the ventricles occur?

How does the rest occur?

A

PASSIVELY

Rest occurs through ATRIAL KICK

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15
Q

How does blood flow into the ventricles occur passively?

A
  • Gravity

- Elastic recoil

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16
Q

What can reduce/extinguish atrial kick?

A

Atrial fibrillation - struggle during exercise

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17
Q

What happens after atrial contraction is complete?

What does this cause?

A

Atrial pressure falls:

Causes a pressure gradient REVERSAL across AV valves

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18
Q

What does the pressure gradient reversal across the AV valves cause?

A
  • Small backflow of blood
  • Valves float upwards before closure (pre-position)
  • Valves close
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19
Q

What are the ventricular volumes in phase 1 (inflow phase)?

Why?

A

MAXIMAL (EDV)

Blood has just been pushed into the ventricles from the atria

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20
Q

What is the LEDV value?

What does this represent?

A

120ml

Represents the VENTRICULAR PRELOAD (stretching of the cells in the ventricles)

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21
Q

What happens to the ventricular preload during exercise?

A

It INCREASES:

Ventricles can contract harder to push the blood out QUICKER

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22
Q

What are the end-diastolic pressures?

A

LV - 8-12mmHg

RV - 3-6mmHg

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23
Q

Why is the end-diastolic pressure in the RV lower than in the LV?

A

1) RV walls are THINNER

2) Pulmonary circuit:
- Alveoli cell walls are one cell thick, with fenesta in between the cells

  • Low pressure so that the plasma doesn’t get pushed out of the vessels and fill the alveoli with fluid –> pulmonary oedema
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24
Q

What happens in phase 2 of the cardiac cycle (isovolumetric contraction)?

A
  • ALL valves are CLOSED
  • Begins with the appearance of QRS complex in the ECG
  • Depolarisation of the ventricles
  • Rate of pressure development in the ventricles becomes maximal rapidly
  • AV valves close when the ventricular pressure is more than the atrial pressure
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25
What does the QRS complex in the ECG represent?
Ventricular DEPOLARISATION
26
What does ventricular depolarisation trigger?
1) Excitation-contraction coupling 2) Myocyte contraction 3) Rapid increase in intraventricular pressure 4) Closure of the AV valves ALSO
27
As well as an increase in pressure and closure of the valves, what else does ventricular contraction trigger? What does this cause?
Contraction of the PAPILLARY muscles with there cordae tendinae Causes tension on the AV valve leaflets - preventing them from bulging back too far into the atria and becoming incompetent?
28
Describe the contraction of phase 2 of the cardiac cycle
ISOVOLUMETRIC Rapid increase in pressure WITHOUT a change in ventricular volume (aortic and pulmonary valves are closed)
29
What is the T wave on the ECG?
Repolarisation of the ventricles
30
What causes the 'C-wave' in the LAP wave?
Slight bulging back of the AV valve into the left atrium - increasing the pressure
31
What happens during phase 3 of the cardiac cycle?
- Aortic and pulmonary valve OPEN | - Ejection of the blood from the ventricles
32
When does ejection from the ventricles occur?
When the pressure in the ventricles EXCEEDS the pressure in the aorta/pulmonary artery
33
What heart sound represents the opening a HEALTHY aortic/pulmonary valve? In a heart with DISEASED valves?
Healthy - NO heart sounds Diseased valved - Heart murmers (can hear the valves close)
34
When is maximum outflow velocity from the ventricles acheived?
EARLY in ejection phase When maximal aortic and pulmonary artery pressures are acheived
35
What happens to the left atrial pressure during ejection from the ventricles? Why?
- Initially DECREASE (atrial base is pulled downwards as it is connected to the ventricle - expands the atrial chamber) - THEN, atrial pressure INCREASE - due to blood flow into the atria from the venous inflow tracts - Pressure continues to rise until the AV valve open at the end of phase 4
36
What occurs in phase 4?
ISOMETRIC RELAXATION: - Pressure DECREASE in the ventricles but no blood flow in the ventricles - When intraventricular pressures fall sufficiently - aortic and pulmonary valves close ABRUPTLY - Blood from the vessels slightly pushes back
37
What is the aortic and pulmonary valve closure associated with? What does this cause?
1) A small BACKFLOW of blood into the VENTRICLES Causes a characteristic NOTCH (diacrotic NOTCH) in the aortic and pulmonary artery pressures 2) And THEN, increase in pressure - diacrotic WAVE 3) Followed by a slow decline in pressure
38
What is the rate of pressure decline in the ventricles determined by? What is this REGULATED by?
The RATE of RELAXATION of the cardiac myocytes (muscle fibres) Regulated by - SARCOPLASMIC RETICULUM that are responsible for rapidly re-sequestering calcium following contraction
39
What is the ability of the cardiac myocytes to relax called?
Lusitrophy
40
What happens to the ventricular pressures in phase 5?
Decrease WITHOUT volume changes (valves are closed)
41
What is the volume of blood that remains in the ventricle after contraction called? What is this volume?
End-systolic volume ~50ml
42
What happens to the ESV during excercise?
Exercising
43
What is the ejection fraction?
The amount of blood ejected from the heart
44
What is the stroke volume?
The difference between the END-DIASTOLIC and END-SYSTOLIC volume About ~70ml
45
What is LAP? What happens to the LAP during phase 4?
Left atrial pressure Continues to rise - due to venous return from the lung
46
What is the peak LAP determined by?
The v-wave on the LAP wave
47
What is phase 6 of the cardiac cycle?
RAPID filling of the ventricles
48
What happens as the ventricles continue to relax?
- Intraventricular pressures will eventually FALL below their respective atrial pressures - AV valves RAPIDLY OPEN and PASSIVE ventricular filling begins
49
Why does the intraventricular pressure continue to briefly fall, even when there is blood flow in from the atria?
Cardiac myocytes in the ventricles are still undergoing relaxation
50
When does the pressure in the ventricles begin to rise?
Once the AV valves are open and the ventricles are completely relaxed
51
What comes immediately after the v-wave on the LAP wave? Why?
y-decent of the LAP Opening of the mitral valve causes a rapid fall in LAP
52
What is the sound of ventricular filling? When is this different?
Normally silent Sound normally heart during RAPID heart filling: - Represents the tensing of the chordae tendineae and the AV ring
53
What happens when the ventricles fill with blood and expand?
- LESS compliant | - Intraventricular pressure RISE
54
What does the rise in intraventricular pressure when the ventricles fill with blood? What does this cause?
Reduces the pressure gradient across the AV valves Reduces the rate of filing late in diastole
55
What happens to the pressures in the atria and aorta when the ventricles fill with blood?
Their pressures fall
56
What are the heat sounds? What produces them?
S1 - Closure of the mitral and triscupid valves S2 - Closure of the aortic and pulmonary sounds S3 - Early diastolic sound. Normally silent
57
Why is the S1 sound normally split?
Mitral valve normally closes slightly BEFORE the tricuspid valve
58
Which heart sound is the longest?
S1
59
Which blood vessel valve closes first in S2?
Aortic valve
60
What does the S1 sound correspond to?
END of diastole | BEGINNING of systole
61
What does the S2 heart sound correspond to?
END of systole
62
What does the S3 heart sound correspond to?
Rapid entry of blood from the atrium to the ventricle
63
Describe the left and right asynchrony?
RIGHT atrial first LEFT ventricle first RIGHT ventricular ejection first

BMS 242 - CVS respiratory (15 decks)

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